(a) Technical Field
The present invention relate to a heating apparatus and method for a fuel cell which reduces a cold-starting time of a fuel cell vehicle, by appropriately heating the fuel cell based on an internal temperature distribution.
(b) Background Art
Typically, in a fuel cell vehicle there is a time delay during cold-starting due to a difference in internal temperature of a stack. More specifically, a non-reacting low-temperature area and a reacting area locally and simultaneously increase in temperature due to ice blockage and the differences in internal temperature of a separator a when the vehicle is starting under cold weather conditions.
Further, the maximum temperature Tmax occurs at the center of a unit cell and the minimum temperature Tmin occurs around the air inlet, where Tmin is about −10˜−5° C. and Tmax is about 10˜30° C., which means there is an area of the fuel cell which is below zero (T <0° C.) (e.g., about 10˜20% of the fuel cell). Further, the lower the external temperature, the larger the difference in the unit cell temperature (maximum 40° C. @ T∞=−25° C.).
Accordingly, some in the industry have proposed heating the frozen fuel cell stack to reduce the ice in the system, but in this process it is difficult to determine the internal temperature distribution. This is because when a stack is heated with a uniform stack temperature distribution, the high-temperature area of the stack is overheated before the low-temperature area is unfrozen, which may cause issues within the stack. Therefore, it was required to develop a technology that reduces the amount of time it takes to cold start a fuel cell vehicle while at the same time appropriately heating the stack based on internal temperature distribution.
Meanwhile, although the distribution of internal temperature of a stack of a fuel cell is an important parameter to determine, only very limited information has been known due to difficulty of mounting a fine internal structure sensor. Therefore, since it is difficult to determine the internal temperature during cold-starting operation, the internal temperature is often estimated from the temperature of the air outlet, but these measurements are purely estimation and are not based on an actual distribution, since currently there is no technology for accurately determining the internal distribution.
Further, most of the technologies were implemented for the entire system of a stack due to the absence of internal information and there is no cold-starting technology for internal differences of a stack. Therefore, it was required to find and heat a low-temperature area by accurately finding out the temperature differences, because supplying more thermal energy to improving cold-starting is a technology that is likely to cause problems relating to local overheating internally.
In a related fuel cell stack a membrane electrode assembly including an electrolyte membrane, an anode, and a cathode, and a separator disposed at both sides of the membrane electrode assembly are included within the stack. A cooling water channel is formed on one side of the separator, and a cooling water intake manifold and a cooling water exit manifold are formed at both ends of the separator, respectively. The cooling water intake manifold is connected with the cooling water channel by a connection channel and has a first space horizontally facing the connection channel and a second space disposed above the first space and trapping bubbles. However, the above described structure does not improve the operability and stability of a fuel cell as efficiently as those skilled in the art may like.
The description provided above as a related art of the present invention is just for helping understanding the background of the present invention and should not be construed as